This background information and publications mentioned below are provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention, and in particular allowing the reader to understand advantages of the invention over devices and methods known to the inventor, but not necessarily public, devices and methods. No admission is necessarily intended, nor should be construed as admitting, that any of the following documents constitute legally citable prior art against the present invention.
After oil and gas wells are drilled, the oil and gas reservoirs or zones of interest need to be completed, namely conditioned by typically a fracking operation, in order to best and most quickly produce oil and gas flow from each particular zone. If the zone of interest requires a type of fracture stimulation, including but not limited to acid fracture or propped fracture, the zone of interest will be isolated to focus the fracture on the zone and to prevent fracture in other zones, which may not be desired. Liner systems can be used prior to conducting the fracture stimulation and can be run in either open hole or cased hole applications.
In the stimulation of directional and horizontal wells, it can be desirable to treat multiple stages in a single zone, known as a cluster, with a single fracture stimulation. It can also be desirable to treat more than one zone with a single fracture stimulation to save time and expense associated with multiple treatments and time spent running tubing and tools in and out of the wellbore.
Various downhole tools have been used to stimulate wells including to treat them in multiple stages, but many of these tools require components within the bore of the liner at each valve which may disadvantageously thereby restrict flow of fluid through the liner during fracture pumping operations, and potentially the further need to mill out such components at each valve location prior to switching to production flow from the hydrocarbon bearing zones. Due to such flow restrictions, pressure drops occur, which result in less efficient operations as there is pressure loss incurred prior to the fracture fluid contacting the zone. Ideally, less pressure drop is desired to conduct a fracture stimulation more efficiently in each stage and in addition. Moreover, it is desirous to have fewer materials/components to mill out within the bore liner immediately prior to commencing production from the hydrocarbon bearing zones.
In this regard, for example, U.S. Pat. No. 8,215,411 teaches cluster opening sleeves for wellbore treatment and utilizes a ball member or plug to open a sleeve at each valve, thereby allowing fluid communication between the bore and a port in the sleeve's housing. This invention requires, however, a ball seat corresponding to each sleeve in a cluster valve, potentially restricting flow. The presence of a ball seat at each valve to be opened, due to the resulting bore restriction at each valve sleeve, creates a significant pressure drop across the cluster valve assembly.
U.S. Pat. No. 8,395,879 teaches a hydrostatically powered fracturing sliding sleeve. Again, such configuration utilizes a single ball, but each sleeve configuration requires its own ball seat.
U.S. Pat. No. 4,893,678 discloses a multiple-set downhole tool and method that utilizes a single ball. Again, each valve requires a seat.
Lastly, US Patent Application Publication No. 2014/0102709 discloses a tool and method for fracturing a wellbore that uses a single ball, each valve with a deformable ball seat. Again, each valve has a valve seat which remains with each valve.